The present invention relates generally to an apparatus for discharging the contents of a sealed container and has particular utility in discharging the contents of a test tube, serum collection tube or the like.
Test tubes are frequently used as collection containers for blood specimens and the like. Typically, an anticoagulant is placed in the test tube, then a blood specimen is withdrawn from a patient and placed into the test tube, and then the test tube sealed with a resilient closure or stopper which is typically formed of rubber. The test tube and its contents are thereafter subjected to temperature variations as well as centrifuging operations. Prior to the invention described in the aforementioned co-pending application, after centrifuging, it was typical to remove the stopper from the test tube such that some of the contents could be transferred to a specimen plate or the like for analysis.
There were, of course, numerous problems associated with the removal of the stopper from the test tube such as the potential for contamination of the blood and exposure of the laboratory technician to any diseases carried by the blood. Of course, there is substantial present concern by the laboratory technician because of potential exposure to the HIV virus, hepatitis or other diseases which may be carried by the blood. The prior application describes a first solution to the aforementioned problem by the provision of a method and apparatus for discharging the contents of a sealed container which includes, in general terms, a holder containing two cannulas, or needles, which are utilized to puncture the rubber stopper or closure of the test tube. One of the cannulas is connected to a compressible bulb or pump, and delivery tube is inserted through the second cannula into the interior of the test tube. Then, upon compressing the bulb, air is introduced into the test tube and the contents of the test tube are pressurized and thus, partially discharged through the delivery tube onto a specimen plate.
Prior to the present invention, however, several further concerns became apparent. Once concern was the degree of force required on the pump or bulb mechanism in order to cause one or more droplets to be discharged. Thus, the laboratory technician desired the ability to actuate the pump only once and, in response a single droplet would be discharged. But it was also required that air be able to enter the interior of the sealed test tube after the droplet was discharged for two reasons, namely, first, to avoid creating a reduction in pressure or partial vacuum within the test tube and second, to fill the compressible bulb so that a second droplet could be discharged.
Yet a second problem arose because collection tubes of the type heretofore described frequently undergo temperature changes in excess of 30.degree. C. For example, a sealed collection tube containing blood is frequently refrigerated, tending to cause a pressure decrease within the collection tube. Also, in a laboratory, the collection tube may increase to room temperature or, if positioned in direct sunlight, to an even greater temperature, thus tending to cause a pressure increase and even an accidental discharge of the test tube contents.